Your Ad HereSolano County is a county located in Bay-Delta region of the U.S. state of California. As of 2016 its population was 440,207. The county seat is Fairfield.HistoryAt the request of General Mariano Vallejo, the county derives its name directly from an Indian Chief, Chief Solano of the Suisunes, a Native American tribe of the region and Vallejo's close ally. Chief Solano at one time led the tribes between the Petaluma River and the Sacramento River. The chief was also called Sem-Yeto, which signifies "brave or fierce hand." The Chief was given the Spanish name Francisco Solano during baptism at the Catholic Mission, and is named after the Spanish Franciscan missionary, Father Francisco Solano.